Process for preparing cyclosiloxanes

ABSTRACT

A PROCESS FOR PREPARING CYCLOSILOXANES HAVING AT LEAST THREE SILICON ATOMS WHICH INVOLVES THE REACTION OF A HALOGEN ENDBLOCKED LINEAR POLYSILOXANE WITH AT LEAST A STOICHLOMETRIC AMOUNT OF AN ALKALI METAL CASRBONATE SALT IN THE PRESENCE OF A SUITABLE POLAR SOLVENT. THE REACTION IS EXOTHERMIC AND IS PREFERABLY CONDUCTED AT ROOM TEMPERATURE.

United States Patent 3,590,064 PROCESS FOR PREPARING CYCLOSILOXANES Charles W. Lacefield, Dow Corning C0rp., Midland, Mich. 48640 No Drawing. Filed July 23, 1969, Ser. No. 844,165 Int. Cl. C071 7/08 US. Cl. 260-448.2E 13 Claims ABSTRACT OF THE DISCLOSURE A process for preparing cyclosiloxanes having at least three silicon atoms which involves the reaction of a halogen endblocked linear polysiloxane with at least a stoichiometric amount of an alkali metal carbonate salt in the presence of a suitable polar solvent. The reaction is exothermic and is preferably conducted at room temperature.

This invention relates to a method for preparing cyclosiloxanes.

The cyclosiloxanes defined herein can be ultimately polymerized to polysiloxanes Which can be employed as elastomers, lubricants and for other uses well known to the art. In addition, certain of the cyclosiloxanes so prepared have been found to possess biological activity which is particularly useful in altering certain physiological functions in mammals.

The present invention relates to a method for preparing cyclosiloxanes of the formula in which R is as above defined, y is an integer of at least 2, and X is a halogen atom selected from the group consisting of a chlorine atom, a bromine atom, and an iodine atom, with (2) at least a stoichiometric amount of an alkali metal cabonate salt, in the presence of (3) a polar solvent, thereafter (B) recovering the cyclosiloxane.

As noted above, R can be an alkyl radical of from 1 to 6 carbon atoms inclusive such as the methyl, ethyl, propyl, isopropyl, butyl, t-butyl, amyl, and the hexyl radical. The alkyl radical may also be halogenated, i.e., with the chlo rine, bromine, or iodine atom.

In addition, R can be an alkenyl radical of from 2 to 6 carbon atoms inclusive such as the vinyl, allyl, methallyl, CH CH CI-I CH=CH, and the radical.

Patented June 29, 1971 R can also be a halogen atom (i.e., the chlorine, bromine, or iodine atom), a phenyl radical, a hydrogen atom, or a 3,3,3-trifluoropropyl radical.

As noted above, z has a valve of at least 3, and X is a halogen atom selected from the group consisting of the chlorine, bromine, or iodine atom.

By the term contacting, it is merely meant that the ingredients (1), (2) and (3) may be physically mixed or reacted in any feasible manner. For example, one may physically mix the polysiloxane (l) and the alkali metal carbonate salt (2) and thereafter add the polar solvent. One may also add the individual ingredients in a suitable container or one may simply add the polysiloxane (l) to a mixture of the alkali metal carbonate salt (2) and the polar solvent 3). In any event, it should be apparent that the ingredients merely be contacted in any generally suitable fashion most convenient under the prevalent circumstances.

At least a stoichiometric amount or more of the alkali metal carbonate salt (2) may be used; however, to best effectuate the purposes of the present invention, it is preferred that amounts in excess of a stoichiometric amount of the alkali metal carbonate salt (2) be employed. It has been found that lesser amounts than those specified above result in extremely poor yields of the desired cyclosiloxanes.

Illustrative of the alkali metal carbonate salts which are suitable include K CO Na CO Li CO Cs CO Rb CO and the like. However, due to its availability and because of its greater reactivity, K CO is obviously preferred.

The polar solvent 3) may be any commercially available polar solvent such as dimethylformamide, dimethylsulfoxide, nitromethane, dimethyl derivatives of diethylene glycols, etc. For purposes of the present invention, acetonitrile is most preferred.

The amount of the polar solvent employed is not particularly critical, however, it is preferred that there be an equal volume or more of the polar sol-vent present based upon the polysiloxane (1), since lesser amounts tend to significantly reduce the yield of cyclosiloxanes which are obtained.

It is to be noted that the defined reaction is exothermic and hence, is preferably conducted at room temperature. More than moderate heating, e.g., 50 C. or more, tends to proportionately reduce the yield of the cyclosiloxanes and also tends to promote random redistribution as 0pposed to the desired selectivity required.

It is to be further noted that the prior art methods for preparing the cyclosiloxanes defined herein, e.g., limited hydrolysis or the use of metal oxides, suffer from certain significant disadvantages. That is, the use of metal oxides results in the formation of by-products which are soluble in the solvent and therefore, complex and costly subsequent steps are necessary if one is to isolate the cyclosiloxanes. If limited hydrolysis is employed, only certain organic substituents can be used because the product of hydrolysis will readily cleave these certain organic substituents, e.g., aromatic substituents, from the silicon atom. For this reason, the limited hydrolysis process can be used only to prepare a limited variety of cyclosiloxanes. In contrast, it has been unexpectedly found that alkali metal carbonate salts function as extremely excellent selective cyclization reactants. The term selective cyclization reactant simply means that these carbonate salts have the unique ability to promote intramolecular condensation of the parent material to form corresponding cyclics while simultaneously avoiding the disadvantages in the prior art methods heretofore related. As noted, it has been found that K CO performs under these conditions in a 'very efiicient manner.

The following examples are illustrative only and should not be construed as limiting the scope of the invention which is properly delineated in the appended claims.

EXAMPLE 1 A 50 ml. Erlenmeyer flask was charged with 10.0 grams (0.072 mole) potassium carbonate (K CO and 45.0 grams acetonitrile (CH CN). Five grams (0.036 mole) of l,5-dichlorohexamethyltrisiloxane was added to the potassium carbonate-acetonitrile mixture. The resultant reaction mixture was continuously agitated employing a magnetic stirrer assembly. After an elapsed time of four hours the decanted solution was neutral to alk-acid paper exposure. Gas liquid chromatography analysis (excluding the resolution for acetonitrile), revealed the following:

Structure: Area percent [(CH SiO] (hexamethylcyclotrisiloxane 76 [(CH )SiO (dodecamethylcyclohexasiloxane) 24 These structures were confirmed by internal standards.

EXAMPLE 2 A three necked two liter flask equipped with an air driven stirrer and vertical condenser was charged with 41.4 grams (0.3 mole) potassium carbonate (K CO and 750 grams acetonitrile (CI-I CN). Added to this potassium carbonate-acetonitrile mixture were 83.1 grams (0.145 mole) 1,13-dichlorotetradecylmethylheptasiloxane (Cl['(CH SiO] (CH SiCl). The resultant reaction mixture was continuously agitated for 24 hours. After this time duration the decanted solution was neutral to alkacid paper exposure. Gas liquid chromatography analysis, excluding the resolution for acetonitrile, revealed 93.1 area percent tetradecylmethylcycloheptasiloxane [(CH SiO] This assigned structure was confirmed by internal standard.

EXAMPLE 3 A 250ml. Erlenmeyer flask was charged with 5.0 grams (0.036 mole) potassium carbonate (K CO and 140.0 grams acetonitrile (CH CN). Added to this potassium carbonate-acetonitrile mixture were 7.7 grams (0.01 mole) 1,l9-dichloroeicosamethyldecosiloxane The resultant reaction mixture was continuously agitated employing a magnetic stirrer assembly. After an elapsed time of approximately 16 hours the decanted solution was neutral to alk-acid paper exposure. Gas liquid chromatography analysis, excluding the resolution for acetonitrile, revealed only one component, eicosamethylcyclodecasiloxane [(CH SiO]1o.

EXAMPLE 4 A three necked three liter flask equipped with an air driven stirrer and vent tube packed with drierite was charged with 56.7 grams (0.41 mole) potassium carbonate (K CO and 1250 grams acetonitrile (CH CN). Added to this potassium carbonate-acetonitrile mixture were 125.0 grams (0.37 mole) 3-phenyl-1,5-dichloropentamethyltrisiloxane The resultant reaction mixture was continuously agitated and followed as a function of time by gas liquid chromatography. The formation of phenylpentamethylcyclotrisiloxane reached a maximum in area percent of 50% of the siloxane products formed. A distilled fraction of 15.1 gram was characterized as follows:

density at 25 C., 10146 refractive index at 25 C., 1.4536

molar refraction: exp. 75.88, theory 76.00 melting point, 6.5 C.

The infrared spectrum was in good accord with the structure for phenylpentamethylcyclotrisiloxane. Nuclear magnetic resonance spectrum afforded the following proton ratios:

Found: Theory: C H CH Si, 3.0; CH Si, 6.0; CH Si, 6.0.

Found: C H Si, 4.8; CH Si, 15.2. Theory: C H Si, 5.0; CH Si, 15.0.

EXAMPLE 5 A three necked two liter flask equipped with an air driven stirrer and vertical condenser was charged with 41.4 grams (0.3 mole) potassium carbonate and 900.0 grams acetonitrile (CH CN). Added to this potassium carbonate-acetonitrile mixture were 93.1 (0.147 mole) 1,13-dichlorophenyltridecylmethylheptasiloxane (Cl (CH Si0 C H CH SiCl) The resultant reaction mixture was continuously agitated for 24 hours. After this time the decanted solution was neutral to alk-acid paper exposure. Gas liquid chromatography analysis, excluding the resolution for acetonitrile, revealed 52.3 area percent phenyltridecylmethylcycloheptasiloxane (C H5CHiS iO[(CHmSiOM The following spectroscopy data recorded for a distilled fraction of the product further confirms the indicated structure. The infrared spectrum was in good accord with the structure for phenyltridecylmethylcycloheptasiloxane. Nuclear magnetic resonance spectrum afforded the following proton ratios:

Found: C H Si, 5.0; CH Si, 39.0. Theory: C l-1 5i, 5.0; CH Si, 39.0.

Found: CH Si, 2.9; (CH Si, 36.1. Theory: CH Si, 3.0; (CH Si, 36.0.

EXAMPLE 6 A three necked five liter flask equipped with an air driven stirrer and vertical condenser was charged with 250 grams (1.81 moles) potassium carbonate (K CO and 3037 grams acetonitrile (CH CN). Added to this potassium carbonate-acetonitrile mixture were 303.7 grams (0.756 mole) 1,S-diphenyl-1,5-dichlorotetramethyltrisiloxane CE: (3113 /CH3 CISiOSlOSiCl C 5115 C H3 C 5115 CH3 CH3 CH S:i-O-S:iOSiiO CoH .COa CaH5 A distilled fraction of 62.4 grams was characterized as follows:

density at 25 C., 1.0714 refractive index at 25 C., 1.5027 molar refraction: exp. 95.58, theory 95.90

The infrared spectrum was in good accord with the structure for a mixture of the cis and trans isomers of 1,5-

*Denotes methyl substitution on silicon containing phenyl.

diphenyltetramethylcyclotrisiloxane. Nuclear magnetic resonance spectrum afforded the following proton ratios:

Found: C H Si, 10.0; CH Si, 12.0. Theory: C H Si, 10.0; CH Si, 12.0.

EXAMPLE 7 A three necked three liter flask equipped with an air driven stirrer and vertical condenser was charged with 81.9 grams (0.593 mole) potassium carbonate (K 00 and 1980 grams CH CN. Added to this potassium carbonate-acetonitrile mixture were 220 grams (0.6 mole) 1,1,7- trichloroheptamethyltetrasiloxane The 'extent of cyclization was followed as a function of time by gas liquid chromatography analysis. At complete disappearance of the 1,1,7-trichloroheptamethyltetrasiloxane 56.7 area percent chloroheptamethylcyclotetrasiloxane was observed by gas liquid chromatography analysis. A distilled fraction of the reaction product yielded the following characterization data:

percent chlorine: found 10.88%, theory 11.18% density at 25 C., 1.0402

refractive index at 25 (3., 1.4016

molar refraction: found 74.15, theory 74.36

The infrared spectrum was in good accord with the structure for chloroheptamethyltetrasiloxane. Nuclear magnetic resonance spectrum revealed the following methyl proton ratios:

Found: CH Si, 0.9; (CH Si, 4.0; (CH Si, 2.1. Theory: CH Si, 1.0; (CH Si, 4.0; (CH Si, 2.0.

EXAMPLE 8 Sixty-two and one-half grams (0.216 mole) of 1,5-dichloro-l-vinylpentamethyltrisiloxane was added portionwise over a 7-minute period to a rapidly stirred slurry of 32.9 grams (0.238 mole) anhydrous K2003 in 1095 ml. (90% by weight) CH CN contained in a 3000 ml. threenecked flask. The extent of reaction was followed by gas liquid chromatography analysis. A gas liquid chromatogram recorded after 107 minutes reaction time revealed that only a trace of the 1,5-dichloro-l-vinylpentamethyltrisiloxane remained and that the cyclotrisiloxane constituted about 82 area percent of the volatiles excluding CH CN. This mixture was immediately taken up in about 1000 ml. of cyclohexane after first decanting it from the solids, K CO and KCl. After several washings with dilute ammonium hydroxide (.l N) and then distilled water, the cyclohexane solution became neutral to alkacid paper and was dried with about 50 grams of Na 'SO filtered and vacuum stripped (approximately 25 C. and 50 mm. Hg) to remove volatiles. This charge (41.6 grams) was then fractionated at reduced pressure in a Todd assembly. Distillation provided 18 grams (0.078 mole) of vinylpentamethylcyclotrisiloxane B.P. 57 C. at 19 mm. Hg, n 1.3965, d 0.9406 gram/ ml., a distilled yield of 36%.

Analysis.-Calcd. for CqHlgSi303 (percent): MR 60.27. Found (percent): MR 59.96.

Gas liquid chromatography analysis of a sample taken from a constant boiling fraction indicated it to be one component. The infrared spectrum of this distilled product was recorded in C01 and CS and showed bands attributable to SiOSi (1015 cm.- SiCH SiCH=CH (1597 cmf and CH indicating a copolymer vinylmethyl-dimethyl cyclotrisiloxane structure. 'Mass spectrometry confirmed the substance as vinylpentamethylcyclotrisiloxane and the mass spectrum showed its first peak at m./e. 234 that has a Si O C H composition. The substance was further identified as vinylpentamethylcyclotrisiloxane on the basis of its proton nuclear magnetic reso nance spectrum recorded in 'CCl The spectrum showed a multiplet at 4.0, 4.2 p.p.m. characteristic of vinyl protons. The spectrum also showed two sharp singlets at 9.822 and 9.862 p.p.m. due to the methyl protons of *CH CHSiCH and Si (CH respectively. The ratio of SiCH=CH protons to SiCH (total) protons was 2.8 to 15.2.

EXAMPLE 9 One-hundred eight grams (0.263 mole) of 1,9-dichloro- 1-hydrogennonamethylpentasiloxane was added portionwise over a 20-minute period to a rapidly stirred slurry of 39.9 grams (0.289 mole) anhydrous K 60 in 1705 ml. by weight) CH 'CN contained in a 3000 ml. threenecked flask. A gas liquid chromatogram recorded 200 minutes reaction time revealed only a trace of the starting chlorosiloxane and that the cyclopentasiloxane constituted about 74 area percent of the volatiles excluding CH CN. The mixture was immediately taken up in about 500 ml. hexane after first filtering away from the solids. After several washings with distilled water the hexane solution became neutral to alkacid paper and was dried with anhydrous Na SO filtered, and vacuum stripped (25 C. and 20 mm. Hg) to remove volatiles. This charge (78.3 grams) was then fractionated at reduced pressure in a Todd assembly. Distillation gave 53 grams (0.149 mole) of nonamethylcyclopentasiloxane, B.P. 74 C. at 6 mm. Hg, 11 1.3945, r1 0.9605 gram/ ml., a distilled yield of 57%.

Analysis.Calcd. for C H Si O (percent): MR 89.10. Found (percent): MR 88.95.

Gas liquid chromatography analysis of a sample taken from a constant boiling fraction indicated it to be one component. The infrared spectrum of this distilled fraction recorded in CCL; and CS showed bands attributable to SiO, SiOSi, SiCH CH, and SiH (2155 cumindicating a cyclopentasiloxane containing SiH. A mass spectrum of this sample confirms the substance as nonamethylcyclopentasiloxane and showed a peak at m./e. 355 for loss of a hydrogen and at m./ e. 341 for loss of a methyl. The substance was further identified as the structure on the basis of its H N.M.R. spectrum recorded in C01 The spectrum showed a multiplet at about 5.2 to 5.4 p.p.m. Characteristic of the SiH protons in the HSiCH moiety. The spectrum showed singlets (not well resolved) at 9.930, 9.909, 9.873 p.p.m. due to the Si (CH and H-SiCH methyl protons. The ratio of S1H protons to SiCH (total) protons was 1.0 to 27.0.

EXAMPLE 10 Thirty-six and seven-tenths grams (0.10 mole) of 1,3 dichloro 1,3 trifluoropropyldimethyldisiloxane and 20.3 grams 0.10 mole) 1,3-dichlorotetramethyldisiloxane were combined and added portionwise with an addition funnel over a 5-minute period to a rapidly stirred slurry of 41.4 grams (0.30 mole) anhydrous K 00 and 513 grams (90% by weight) CH CN contained in a 2000 ml. threenecked flask. Gas liquid chromatography was used to folrecorded after 4 hours reaction time revealed that the starting 1,3-dichlorodisiloxanes had been reacted and the following area percentages of cyclotetrasiloxanes indicated (excluding CH CN): [(CH SiO]4, 17.5%;

CH3 (C F sCHzCHzs i O )4 3 4. 8 The reaction products, [(CH Si 4 and CH3 (C FsCHzCHzs i O )4 were identified by gas liquid chromatography spiking methods with internal standards and the copolymer cyclic was ascertained by logical chemistry and its gas liquid chromatography retention time. This mixture was immediately taken up in cyclohexane (600 ml.) after first decanting it from the solids, K 00 and KCl. After several washings with distilled water, the cyclohexane solution became neutral to alkacid paper and was dried with about fifty grams of anhydrous Na SO filtered, and vacuum stripped to remove cyclohexane (25 C. at 50 mm. Hg). This charge (46.8 grams) Was then fractionated at reduced pressure in a Spinning Band Assembly.

EXAMPLE 1 1 When the following polysiloxanes were substituted for the polysiloxane of Example 6 and the preparation was as described therein, the indicated cyclics were obtained CH; CsHs CH3 CH3 (CH )gCHs CH3 CH3 CH3 EXAMPLE 12 in which R is selected from the group consisting of an alkyl radical of from 1 to 6 carbon atoms inclusive, a halogenated low the extent of reaction. A gas liquid chromatogram alkyl radical of from 1 to 6 carbon atoms inclusive, an alkenyl radical of from 2 to 6 carbon atoms inclusive, a halogen atom selected from the group consisting of a chlorine atom, a bromine atom, and an iodine atom, a phenyl radical, a hydrogen atom and a 3,3,3-trifluoropropyl radical and z is an integer of at least 3, comprising (A) contacting (l) a polysiloxane of the formula in which R is as above defined, y is an integer of at least 2, and X is a halogen atom selected from the group consisting of a chlorine atom, a bromine atom, and an iodine atom, with (2) at least a stoichiometric amount of an al kali metal carbonate salt, in the presence of (3) a polar solvent, thereafter (B) recovering the cyclosiloxane. 2. The method as recited in claim 1 in which the alkali metal carbonate salt (2) is K 00 3. The method as recited in claim 2 in which the polar solvent (3) is acetonitrile.

4. The method as recited in claim 3 in which the polysiloxane (l) is of the formula Cl (CH SiO] (CH SiCl 5. The method as recited in claim 3= in which the polysiloxane (l) is of the formula on (CH3 SiO] 6 (CHshSiCl 6. The method as recited in claim 3 in which the polysiloxane (1) is of the formula 7. The method as recited in claim 3 in which the polysiloxane (1) is of the formula 8. The method as recited in claim 3 in which the polyslloxane (1) is of the formula 9. The method as recited in claim 3 in which the polysiloxane (1) is of the formula 10. The method as recited in claim 3 in which the polysiloxane (l) is of the formula 11. The method as recited in claim 3 in which the polysiloxane (1) is of the formula 12. The method as recited in claim 3 in which the poly- Referel l s Cited siloxane (1) is of the formula UNITED STATES PATENTS f E 3,484,469 12/1969 Guinet et a1. 260448.2-E ClSiOSiOSiOSiOSi-Cl 5 5 5 5 (3H3 5 JAMES 'E. POER, Primary Examiner 13. The method as recited in claim 3 in which the SHAVER, Assistant Examiner polysiloxane 1) is of the fonnula CL (CHfizCFa CH3 CH3 CH3 260448.2R

C1-Si-OSi-O-Si-OSi01 10 I I CH3 CH3 CH3 CH3 

